Electronic Waste, or e-waste as it is commonly known now, is fast becoming a dominant factor contributing towards polluting the earth in all its physical forms i.e. air, soil and water. World over there is a concerted effort being put to reduce, reuse and recycle (preferably in that order) the electronic devices that have reached an end-of-life of their intended purpose or market. Towards this effort, the governments of various developed and developing countries as well as commercial interest groups are actively involved in developing policies and technologies that can efficiently address this problem and generate resources from e-waste such that it becomes an economically viable model for all.
From a recycling perspective of handling e-waste, most e-waste recyclers use manual, physical or chemical or a combination of all three to extract precious, rare-earth and industrial metals as well as non-metals like PVC, plastic, paper, glass, oil, fuel etc.
Printed Circuit Boards, or PCB as commonly known are one of the most harmful parts that constitute to anywhere from 10% to 60% of any electronic device. If dumped in landfill or processed in non environmental friendly methods, they constitute bulk of the polluting matter in any electronic device by volume or weight.
Since electronic waste recycling is the exact opposite of the process of electronic manufacturing as a process, there cannot be any control on the quantity, shape, size, and type of material of the input. This makes the processing of the PCB very particularly difficult especially with respect to separation of the individual components on it. The various components on the PCB are firmly fixed to the copper pads of the PCB either by soldering it directly or mechanically fixing it to the PCB.
In some of the currently prevailing methods of handling e-waste, the whole of the PCB is processed together. While this process of metal extraction may be acceptable in current circumstances, the recovery efficiency is very limited because of the mixed nature of the PCB and its components.
U.S. Pat. No. 4,874,486 describes process of recycling of electrical batteries, assembled printed circuit boards and electric components. The process comprises heating of the whole PCB as such at very high temperature and then chemically processing the molten slag. The disadvantages of the process include low efficiency due to less recovery of precious metals. Further, the recovered metals are highly impure and cannot be utilized for making standard quality product again.
U.S. Pat. No. 5,683,040 teaches method for recycling waste from PCB assemblies. The process involves of removal of contaminants from PCB, mechanically pre comminuting the PCB to obtain particles of size not more than 30 mm and then cryogenically embritting the particles thus selected. The main drawback of the process is that only components being able to be recycled are those having size less than 30 mm and hence limiting the scope of applicability and limiting the recyclability of complete PCB.
U.S. Pat. No. 6,234,317 discloses device for sorting raw, pretreated or recycled bulk material. The device is of lesser utility in recycling purpose as the main function of component removal from PCB has to be performed separately.
In order to overcome some of the limitations, one of the ways is to put everything, irrespective of the differences in shape, size, and type of material, into a specialized smelter and separate the metals by parts by smelting in lead, copper, silver etc. However this process requires a large furnace, large smelter and large quantity of raw materials to feed its process continuously for it to be economically viable. In this process it also impossible to recover any item on the PCB that can be reusable.
The PCB contains a multitude of metals in the form of building material for electronic parts and components. Each of these metals has different physical and chemical properties. For example, they have different melting points, different physical structure and different reactions to chemicals. As they react differently to chemicals and can also form alloys for the purpose of the electronic component. Therefore any one process for separation does not yield the best results.
In order to resolve this and as an alternative, this invention provides a method and apparatus for preprocessing of the boards and removal of all the components and then separating them into broad categories and processing each type by a more efficient method to do a better recovery irrespective of the quantity because the metal recovery can be targeted based on the known chemical content and physical profiles of component material and the yields can be significantly higher. The other advantage to this invention is to recover many reusable parts from the PCB that can be used as-it-is without any effect on the individual usability specifications of the recovered items.